Summary: A sinonasal drug delivery system consisting of freeze-dried thermoresponsive hydrogel with degradable microspheres (MSs), called FD-TEMPS (Freeze Dried - Thermogel, Extended-release Microsphere-based delivery to the Paranasal Sinuses), was developed. Measurements of glass transition temperatures of the maximally freeze concentrated solutions informed optimization of the thermogel. Using a higher molecular weight polyethylene glycol (2000 Da) with poly(N-isopropylacrylamide) resulted in freeze-dried gel with a brittle texture, porous structure, and low residual moisture (<3%). When combined with poly(lactic-co-glycolic acid) MSs and freeze dried, FD-TEMPS exhibited enhanced shelf-stability with maintained MS morphology and initial release kinetics following 6-weeks storage under ambient conditions. Furthermore, FD-TEMPS remained in place after application to a simulated mucosal surface, suggesting that it could be more uniformly distributed along the sinonasal mucosa. Freeze drying enables this sinonasal delivery system to be stored as a ready-to-use product for better ease of clinical translation without compromising thermoresponsive or sustained release characteristics.
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